Most bacteria originated from either oral or nasal cavities.

Related

THURSDAY,
May 31, 2012 (MedPage Today) — You may want to clear
out your workspace and break out the disinfecting wipes: Your area is teeming
with bacteria, most of which is human in origin, according to a new
study.

More
than 500 bacterial genera were identified based on an analysis of viable
heterotropic bacteria cultivated off office space surfaces in three cities.
There were highly significant differences in bacterial abundance among
surfaces, genders, and cities, reported Scott Kelley, PhD, from San Diego State
University, and colleagues in PLoS One.

Chairs
and phones were the most contaminated surfaces while spaces inhabited by men
were more germ-ridden compared with areas where women worked, they noted. Also,
offices in San Francisco tended to be less contaminated than offices in New
York and in Tucson, Ariz.

However,
they pointed out that most of the human-associated bacteria were
"commensals," which indicates a symbiotic relationship between two
organisms, where one organism benefits but the other is neutral.

"Humans
are spending an increasing amount of time indoors, yet we know little about the
diversity of bacteria and viruses where we live, work and play," Kelley
said in a statement. "This study provides detailed baseline information
about the rich bacterial communities in typical office settings and insight
into the sources of these organisms."

Previous
studies of office buildings have reported 106 bacteria
per cubic meter in an ever-changing microbial environment. In 2008, Finnish researchers discovered hundreds
of unique microbial lineages (OTUs) at just two different office buildings
(BMC Microbiol online, April 8, 2008).

For
the current study, the authors combined culture-based cell counting and
multiplexed pyrosequencing of environmental ribosomal RNA gene sequences. This
"deep-sequencing approach" allowed for broader sampling and more
detailed sequencing. They chose offices in the three cities because they
offered diverse climate regimes.

They
swabbed about 13 cm2 of the same surfaces in every
building: chairs, phones, computer mice, computer keyboards, and
desktops.

They
found that human oral and nasal cavities as well as skin were the primary
sources of office bacterial contamination. Proteobacteria (Salmonella,
Helicobacter) was the most common, followed by Firmicutes, Actinobacteria, and
Bacteroidetes. Together, these groups made up nearly 90 percent of the
sequences, the authors said.

Bacteroidetes
is associated with the human digestive tract and the genera does include
pathogens, but the sequence information that the authors collected could not distinguish
bacterial strains or species.

As
for the differences in contamination levels based on gender, Kelley's group
offered two possible explanations: Men are
perceived as being less hygienic
than women (washing their hands less frequently) and they also may shed more
bacteria into the environment simply because they are generally larger than
women.

Other
bacterial genera noted in the study were associated with soils and with some
environmental sources such as microbacteriaceae.

Finally,
the samples from Tucson were quite different than those from New York and San
Francisco, probably because of the desert soils. For instance, bacteroidetes
and Cyanobacteria were essentially absent in the Tucson samples but were seen
in samples in the other cities.

The
549 bacterial genera found in this study was much higher than the 283 unique
OTUs discovered in the Finnish study, the authors said, most likely because of
broader sampling and deeper sequencing. But the results were in line with
studies on airplane bacterial contamination
(ISME Journal online, February 7, 2008).

While
the bacteria levels reported in the current study would probably only pose a
problem for people who have severely compromised immune systems, these findings
in "nominally 'healthy' buildings"could be useful for identifying sick building syndrome, the authors
said.

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